Failing to Read Nested Data From Firebase Database

Question

I am sending "Appetizers and Snacks" which is in name key from one activity 1 to activity 2.

In activity 2,the data received is simply :

Answer 1

Instead of this:

databaseReference = FirebaseDatabase.getInstance().getReference("All Categories").child("name").orderByValue().equalTo(received_id).getRef();

You'll want to use:

Query query = FirebaseDatabase.getInstance().getReference("All Categories").orderByChild("name").equalTo(received_id);

So:

1. Use orderByChild("name") to tell the database to order all child nodes on the value of their name property.
2. Use equalTo(...) to then filter down the sorted data.
3. Remove the getRef() as that actually undoes all your query buildin.

To then read the data, do:

query.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        if (dataSnapshot.exists()) {
            for (DataSnapshot categorySnapshot: dataSnapshot.getChildren()) {
                for (DataSnapshot recipeSnapshot: categorySnapshot.child("recipes").getChildren()) {
                    DetailModel p = recipeSnapshot.getValue(DetailModel.class);
                    detailModelList.add(p);
                }
            }

            detailAdapter = new DetailAdapter(DetailCategory.this, detailModelList);
            recyclerView.setAdapter(detailAdapter);
            progressBar.setVisibility(View.INVISIBLE);
        } else {
            Toast.makeText(DetailCategory.this, "No data available !", Toast.LENGTH_SHORT).show();
            progressBar.setVisibility(View.INVISIBLE);
        }
    }

So:

1. Listen to the entire query we just created.
2. Then loop over the children of recipes of each node we get back in the snapshot.

Answer 2

    databaseReference = FirebaseDatabase.getInstance().getReference();
    val ref = database.child("All Categories").child("0").child("recipes")
    
   
    val valueEventListener = object : ValueEventListener {
    override fun onDataChange(dataSnapshot: DataSnapshot) {
         val recipes = dataSnapshot.getValue(Recipes::class.java) // recipes model reading
    }

    override fun onCancelled(databaseError: DatabaseError) {
        
    }
}
ref.addListenerForSingleValueEvent(valueEventListener)